Dual seal system for roots blower

Abstract

This invention pertains to a dual seal system for preventing cross-contamination of the bearing compartments from the process cavity, and the process cavity from the bearing compartment, within a Roots blower. The seal system comprises a inner floating seal having a diameter slightly larger than the shaft so that there is a clearance between the shaft and the seal and a face seal embraced at an outer end of the shaft in fixed communication with the shaft and adapted for rotation. A fluid inlet passage is disposed between the floating seal and the face seal, and permits fluid to be introduced to the seals and in the case of the floating seal pass through the clearance space between the floating seal and shaft and then into the Roots blower cavity.

What is claimed is: 
     
       1. In a Roots blower comprising: a housing having an inlet and outlet port and walls defining a cavity therein;   closure plates secured at the ends of the housing for enclosing said cavity;   a pair of parallel shafts having cylindrical portions extending transversely between said inlet and said outlet port and extending through said closure plates;   a bearing compartment embracing said cylindrical portions of said parallel shafts and external to said cavity and adjacent to said closure plates;   bearings disposed within each bearing compartment and embracing said cylindrical portions for permitting rotation of the shaft therein;   lubricating means for said bearings while in said bearing compartment;   sealing means between the cavity and bearing compartment for preventing leakage of contaminants into and out of said compartment; and   lobed impellers disposed within said cavity and mounted on said shaft in coacting relationship with each other and the walls of the cavity wherein in operation a gaseous fluid is introduced through the said inlet port, trapped and compressed between adjacent lobes of each impeller and the walls of the cavity and then exhausted at some higher pressure through said outlet port, the improvement residing within said sealing means which comprises in combination:   (a) a seal housing disposed between said bearings and said closure plate;   (b) a floating seal disposed within said seal housing and embracing a cylindrical portion of said shaft proximate said closure plate, said floating seal having a diameter slightly larger than said shaft thereby providing a circumferential clearance space between it and said shaft;   (c) a face seal disposed within said seal housing and embracing a cylindrical portion of said shaft, said face seal proximate said bearing;   (d) a fluid inlet passage disposed within said seal housing and in communication with said floating seal and said face seal, said passage permitting continuous flow of gas through said clearance space between said floating seal and said shaft and into said cavity and flow to said face seal;   (e) an exterior mating ring disposed about said shaft and proximate said face seal, said exterior mating ring having a contact surface designed for seal contact with said face seal, and adapted for rotation relative to said face seal, and   (f) means for urging said face seal and said external mating ring toward each other to provide sealing contact therewith.   
     
     
       2. The Roots Blower of claim 1 wherein said face seal is urged outwardly from said seal housing and toward said exterior mating ring. 
     
     
       3. The Roots blower of claim 2 wherein said external mating ring is in fixed contact with said shaft and thereby rotates with said shaft.